The present invention relates generally to lacing machines and more particularly to methods and apparatus for protecting a lacing machine operator during machine processing of dynamoelectric machine stators.
Lacing machines generally employ a cooperating pair of moving members or elements, one dispensing cord, and the other (called a hook or needle) selectively engaging the cord in loops to translate those loops relative to the workpiece and the dispensing element to tie or stitch the cord progressively about the workpiece. Thus, for example, while lacing end turns of dynamoelectric machine stators, the lacing needle frequently executes a staggered reciprocating motion generally perpendicular to the stator bore axis alternately between the end turn portions and the stator core side surface and beyond the end turn portions. In synchronism with needle motion, the dispensing element presents a section of cord to the needle during each reciprocation and this, coupled with appropriately timed rotation of the needle about its axis of reciprocation to pick up and drop the loop, allows an interlocked chain of such loops to be formed. Periodic indexing of the stator about its bore axis allows such a chain of loops to be formed about the entire end turn region of the stator. Apparatus and methods for tying coils are described, for example, in Gawthrop et al, U.S. Pat. Nos. 3,659,337; Fields et al, 3,813,754; and Habegger et al, 3,824,940, all of which are assigned to the assignee of the present application. Other patents relating to lacing machines include Frederick, U.S. Pat. Nos. 3,440,979 and Frederick, 3,685,470 which are assigned to Link Engineering Company. The entire disclosure of each of these above-mentioned patents is specifically incorporated herein by reference.
In such coil tying methods and apparatus, it is frequently desirable that the operator actively participate in the tying process, for example by holding a small workpiece in the vicinity of the moving lacing needle so that the workpiece may be tied to the end turn portions during the lacing operation. Frequently, such a workpiece will comprise a small identification tag or additional winding insulating material.
The potential operator hazards associated with lacing machines of this general type have been recognized and the safety feature frequently employed as an option on commercially available lacing machines comprises a photoelectric cell-light source arrangement where the light pathway between the source and cell traverses a region between the operator and the lacing machine needle path. If the operator reaches into the area of the needle path, the light pathway is interrupted and machine operation impeded. These electric eye safety devices have been less than completely satisfactory for several reasons. The source-sensor light pathway is limited in size and the potential for an operator to intentionally or accidentally reach around the light pathway and into a hazardous region is ever present. To adapt to various installation situations, the sensor and light source are typically adjustable, raising frequent misalignment problems. The opportunity for active operator participation in the lacing process, such as for example, to hand position a small workpiece, such as insulating material or an identification tag, in the region of the needle path during lacing, to attach that workpiece to the structure being laced by the lacing machine, is quite restricted since the operator in attempting such active participation will frequently inadvertently block the light pathway, stopping the machine.